Practice question

Environment-sensitive genic male sterility category includes conditional nuclear sterility reversible by external cues, divided into thermo-sensitive GMS TGMS where sterile to fertile transition governed by temperature threshold during young panicle stage, and photoperiod-sensitive PGMS governed by day length threshold perceived via phytochrome signaling. Some lines respond to both termed PTGMS. Examples: rice TGMS line Annong S-1 becomes sterile above 24C, fertile below, while NK58S PGMS sterile under long days greater than 13.5 h fertile under short days. Genes identified include pms3 encoding long noncoding RNA whose promoter methylation photoperiod regulated, and tms5 encoding RNase Z. Conditional system enables two-line hybrid breeding: line multiplied as fertile under permissive environment and used as sterile parent under restrictive environment, reducing need for maintainer B-line simplifying breeding. This understanding supports competitive exam preparation for NEET, GATE and CSIR NET concepts linking genotype with phenotype through molecular pathways involving transcription factors, hormones and metabolic enzymes that regulate development, adaptation and reproductive biology in applied breeding programs.